The present invention relates to a novel transducer head assembly for use with a multi-track record disk. The invention also relates to a method and apparatus using the novel transducer head assembly for recording, reproducing or erasing data with respect to the record disk, and further, to a method of using such assembly for initializing a virgin record disk.
Record disks are commonly used for storing data in computers and other data processing systems. Such record disks are provided on both faces with a layer of a magnetizable material for recording the data in the form of a plurality of spaced, annular tracks. Some disk systems, or disk files as they are frequently called, include a plurality of such record disks stacked on a common spindle and driven by a common drive, whereas others include only one record disk. Because of the expense involved in providing a head for each track, most systems use one head per disk, which means that the head must be very accurately positioned to align itself with the selected track with respect to which the data is to be recorded, reproduced, or erased.
In order to obtain the maximum storage capacity per disk, a large number of tracks are provided on each surface, for example 200 tracks per inch or more. A factor limiting the track density, however, is the precision with which a head can be positioned with respect to a selected track. Positional inaccuracies may arise from a number of factors, including spindle eccentricity; temperature-coefficient variations with respect to the disk, base, head and transducer; nonlinearity in the transducer; and setting-up errors. If the head is not precisely positioned on a track from which recorded data is to be read, the signal level will be reduced and errors may therefore occur.
A number of techniques have been devised for reducing such positional inaccuracies. One system utilizes an arrangement which generates a positional wave-form (e.g., sine-wave) as the head moves towards the spindle, the zero crossings defining the track positions. Such a system, however, does not take into account effects external to the disk, such as dimensional variations caused by unequal temperature-coefficients. Another technique utilizes "dedicated tracks", in which the head is aligned with data prerecorded on special tracks on the record disk. These systems, however, require that a substantial recording surface be allocated to the dedicated tracks and therefore deprive such surfaces from being used for recording the informational data. They are therefore used mostly with multi-disk systems in which one disk includes the prerecorded positional data.